Contact structure for electric switches



C. D. AINSWORTH CONTACT STRUCTURE FOR ELECTRIC SWITCHES De.11,192s. 1,694,612

' Filed May 29. 1925 1| g jvve-fo. -:3.1.2. m nl) I I 211 Patented Dec. 11, 19728. y

' UNITED sTATEs PATENT OFFICE.

cHEs'rEa D. AINsWoaTH,

OF WOLLASTON, MASSACHUSETTS, ASSIGNORgBY MESNE AS- SIGNMENTS, TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS. y

CONTACT STRUCTURE FOR ELECTRIC SWITCHES.

Application ledlay 29, 1925. Serial No. 33,812.

This invention relates to electric switches adapted to carry relatively high values yof current and has for an object an im roved construction of movable switch mem er, or brush member, in which the magnetic 'eff fect of the current traversing it has reduced tendency to move the brush'members away from contact with its cooperating stationary switch members.y

In the usual type of brush member, which brush member may be the current, in passing down oneleg of the U and up the other leg, sets up a magnetic effect which acts upon the legs of the U tending to forcerthem outwardly and away from f the contact with their cooperating stationary y switch members, or, at least, .the contact pressure may be reduced to such a low value, by reason ofthe magnetic effect, that harmful heating-or even arcing at the `contact junction may be set up.

In carrying out the above object of the 1nvention, I provide a laminated brush member of such shape that the magnetic effects 35 current traversing the brush member, in the various portions thereof, tend to .neutralize each other so that the contact pressure of the brush against the stationary switch members may remain substantiall the current traversing the rush, or' may even be increased.

A further object' of the-invention is generally to improve the constructionand operation of electric switches and the current-carrying components thereof.

Fig. 1 is a side elevation of the stationary switch members, and the movable or brush member of an electric switch embodying the invention.

Fig. 2 is an end elevation of the movable switch member of Fig. 1.

Fig. 3 is a sectional view of Fig. 1.

Figli is a side elevation of the brush member of the movable switch member of Fig. 1. Fig. 5 is a diagram illustrating the manner in which the magnetic field due to the current traversing the brush and stationary switch members acts upon the brush member. The electric switch embodying the invention may comprise stationary switch members which may include the relatively masalong line 3-3 sive and preferably solidstudsl. Relative of more or less U-form,

of the l uninuenced by 'massive fixed contact members 11 may be secured to the lower ends of said studs in good electrical contact therewith and the lower ends of saidffixed contact members ma `ter- Inmate in fiat contact faces 12 whic are adapted to be engagedby the brush member of the movable switch member. Saidcontact members may also be vformed or provided with inwardly directed toe portions 13 which are eccentric with respect to the vertical axis A of the stationary switch members, and the greater portion of the contact face of the movable switch member is or may be arranged with the contact members 11 at said toe portions.

The movable switch member may include the supporting rod 14, to the lower end of which the laminated brush member 15 is adapted to be secured. For this purpose, a brush-supporting member is provided, which member is or may be formed with the two complemental portions 16v and 16 and the flat feet 17 and 17a; and said brush-supporting member is or vmay be clampedabout the lower end of said rod 111 by suitable means as the screws 18. Two identical brush members 15 are here shown as supported by said brush rod; and said brush members may be secured in spaced relation on the feet 17 and 17a of said brush supporting member by .suitable means as the bolts 19, which bolts are or may be passed through holes in said brush members and be screw threaded in the feet of said brush supportingmember.

In accordance with this invention, the brush member yis formed of a plurality of relatively thin leaves or laminae shaped into the form more particularly shownin Fig. 4. The brush member comprises the bottom `connect-ing and separating portion 20 and the substantially vertical side-portions or legs 21, each of the side portions being refiexed upwardly into substantially right angles with respectto the horizontalbottom portion 20. The side portions 21 vare reflexed outwardly or gent end portions 22, which end portions may Vcomprise' he contact-terminals ofthe brush member. The upper faces of said contactyterminals are formed with the contact faces 23, which faces are adapted to engagewith the .cont-actl faces v12 of the fixed contact members 11 thereby to complete the' circuit are provided with the diver-l through the switch. Said contact faces 23 are preferably inclined somewhat upwardly and outwardly, or given a rake, as may be more or less common practice. Preferably the divergent end portions 22 of the outer iaminte are of longer extent than the corresponding end portions of the inner laminas as is clearly illustrated in Fig. 4. The angle B which the end portions 22 of t-he laminas malte with respect to the intermediate portions or legs il .he brush members may be of some impo .ance and, preferably, said angle B is about equal to or less than the angle formed between said end portions 22 of the laminal and the current lines in the fixed contact member ll leading to the lamime.

The brush member asl thus described is preferably assembled on the brush-supporting member of the switch rod M with a relatively heavvfv resilient leai 25 of spring material conforming with the innermost lamina of the brush member and extended upwardly therealong to the outward bend thereof; and said spring leaf may be disposed between the brush member and the leet of the brushsupporting member. A similar strip of flexible spring material 26 inay be disposed about the brush member in contact with the outermost lamina thereof and said member 26 may have its upper end portions 27 reflexed outwardly and lie along and conform with the end portion 22 of' the outermost lamina whereby to provide substantial supportl for the contact-terminals of the brush. Said member may be interposed between he brush member and the heads ot' the bolts 19.

A strain member is or may be disposed about and engage the brush member in the angles lying between the port-ions 21 and 22 ot the brush; and said strain member is adapted to support said brush, or, more specifically the legs 2l thereof, against lateral outward or divergent movement due to the magnetic effect of the current traversing the brush and about. the angle C subtended bctween the legs 2l and the horizontal connecting and separating portion Q2 of the brush; and also against spreading due to the mechanical pressure exerted on the brush member when the switch is closed. Said stra-in meniber may include tubular rollers 30 which preiei'aljily are formed of insulatingr material, as libre. Said rollers are adapted to be approximately co-extensive with the width of the brush member or.v as here shown. with the width oi both brush members. Relatively strong pins 3l, preferably formed of steel or some sin'iilar material. are extended through said rollers; and the ends of said pins are adapted to project beyond said rollers, and also said brush members, on opposite sides thereof. Insulating washers 33 may be disposed on the ends of said pins and are adapted to overlie the brush members, mainly for the purpose of insulating the tie-members 34 from the brush members. Said tie members 34 are extended on opposite sides of the brush members between said pins 31 and are or may be formed with elongated slots 35 in the ends thereof. through which slots said pins 3l are loosely extended. Suitable means as Cotter pins 3G muy be passed through said pins 31 whereby to secure the components ot' the strain member in operative relation with each other. The dimensions of the strain member are or may be such that the insulating rollers 30 thereof bear normally with some degree of in'essure against the sides of the brush members. Said strain member is or may be free to move vertically, or float, on the brush member and may be secured thereto against unintentional detachment therefrom by suitable means as the stop members 40, which members may comprise screws threaded into the feet 17 and 17 of the brush-supporting member and extended laterally therefrom into a position beneath the tie rods 34 ot' said strain men'iber. The magnetic effect of the current traversing a bent conductor is to straighten the conductor or bring the bent portions thereof into alignment. The magnetic effect of the current traversing the brush meniber about the angles C is to tend to move the legs 2l of the brush member outwardly or into alignment with the horizontal connecting and separating portion 20; and said strain member is adapted to resist this tendency and support the legs against such magnetic effect of the current. The magnetic effect of the current in other portions of the brush member is best illustrated in Fig. 5, in which F may represent an inner brush lamina and G an outer brush lamina of the brush memljier. The contact terminal Q2 ot said outer brush lamina G is here shown as making contact with the fixed Contact member ll in substantially the axis A of the fixed switch member,- and the path or line of current traversing the switch member and entering the tip oi the brush lamina G may lie in or be substantially parallel with said axis A. By reason oi? the angle H subtended between the end-terminal 22 of the lamina G and the axis A or path of current in the .fixed switch men'iber, the resultant magnetic effect is or may be in such a direction as to tend to move the tip of the brush lamina outwardly in the direction of the arrow J. thereby to reduce the contact pressure of the lamina against the fixed rontact member. The magnetic eliect o't' the current in traversing the brush lamina, about the angle B, is to move the end-terminal of. said lamina in the opposite direction,` or in the direction ot' the arrow K. Since the angles H and B are or may be substantially equal, the two forces may more or less neutralize each other and the original cont-act pressure, at least, Will not be reduced.

It is apparent that if angle B is made less than angle H, the resultant effect of the current acting upon the `end-terminal of the brush member is in a direction to move the tip inwardly or increase the contact pressure thereof.

The magnetic effect of the current traversin the inner brush laminae F about the angle B 1s also to move the tip 22 of said lamina inwardly as indicated by the arrow M and thereby to increase the contact pressure of said lamina. against the fixed contact member. The path of current in the fixed contact? member 11 with respect to said inner brush lamina F may be more or less as indicated by the dotted line Ny and the angle O subtended between said path of current and the tip 22 of the brush lamina may be greater than the angle B. The magnetic effect of the current as it passes into said brush lamina F thereby may act in a direction to increase the contact preure of the lamina, or in thedirection of the arrow M.

With the brush member as thus arranged, it may be seen that the magnetic effects of the current traversing the various angularly-related portions or sections on the brush member in series are more or less neutralized; or with the specific` arrangement of contact and brush members herein illustrated, the inner brush laminas may be forced into increased cont-act pressure with the fixed switch member with increased values of current therein while the outer lamina of the brush member may be forced inward with lesser effect or at the least the tendency toward reduced contact pressure is reduced.

The structure may be otherwise modified without departing from the spirit of the invention.

I claim:

1. A brush member for an electric switch, said brush member composed of laminations each having a bottom. connecting and separating portion, and integral opposed and substantially vertical legs extended a substantial distance above said bottom portion, said legs having contact terminals which are divergent from each other.

2. A brush member for an electric switch, said brush member having a bottom connectlng and separating portion, opposed and substantlally vertical legs and divergent contactA terminals, and a strain member connecting said legs and arranged to support them against divergent movement.

3. A brush member for an electric switch, said brush member having a bottom connecting and separating portion,opposed and substantially vertical legs and divergent contact terminals, and a strain member connecting said legs at the junction thereowith ysaid divergent contact terminals and arranged to restrain said legs against divergent movement.

4. A brush member for an elec-tric switch,

said brush member having a bottom connecting and separating portion, opposed and substantially vertical legs rising from said connecting and separating portion, and said legs having divergent contact terminals, and a strain member connecting and iioating on said legs and arranged to restrain them against divergent movement. y 5. A brush member for an electric switch, said brush member having a bottom connecting and separating portion, opposed and substantially vertical legs rising from said connecting and separating portion, said legs having divergent Contact terminals, and an insulated strain member connecting said legs and arranged to restrain them against divergent movement.

6. A 'brush member for an electric switch, said brush member having a. bottom connecting and separating portion, opposed andsubstantially vert-ical legs rising from said connecting and separating portion, said legs having divergent contact terminals, a strain member connecting and floating on said legs and arranged to restrain them against divergent movement, and means to restrict the ioating movement of said strain member.

7. A brush member for an electric switch, said brush member having a'bottom connecting and separating portion, opposed and substantially vertical legs rising from said connecting and separating portion, said legs having divergent contact terminals, insulating rollers disposed at the junction of said legs and contact terminals, and tie-members connecting said rollers, whereby to restrain said legs against divergent movement.

8. A brush member for an electric switch, said brush member having a bottom connecting and separating portion, opposed and substantially vertical legs risingyfrom said counecting and separating portion, said legs having divergent contact terminals, a brush-supporting member connected with said brush member intermediate said legs, a strain member oating on and connecting said legs to restrain them against divergent movement, and means carried by said brush-supporting member arranged to engage said strain member and limit the movement thereof.

9. A brush member for an electric switch composed of laminas each having a horizontal body section and opposed parallel upstanding yieldable end-sections which have at their upper free ends outwardly-divergent toe-scctions keach terminated in a generally horizontal contact face.

In testimony whereof, I have signed my name to this specification. c

AINSWORTII. i

CHESTER D. 

